The present invention is directed to an apparatus for the mass electroplating of bulk goods, particularly for the electro-deposition of aluminum from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte. The apparatus includes a plating tank for the acceptance of an electrolyte, a goods carrying dish being mounted to rotate on a incline axis in the plating tank and being immersed in the electrolyte, at least one disk-shaped anode dipping into the electrolyte and being aligned to be mainly parallel to a floor of the goods carrying dish and the goods carrying dish having at least one dog or ridge for spreading the goods on the floor of the carrying dish as the dish rotates.
In mass electroplating of bulk goods, the goods for galvanization must be held together so that during the galvanic processing, every individual part has electrical contact. On the other hand, the goods for galvanization should be spread out as far as possible so that the metal deposition can occur on the largest possible surfaces of the goods and an optimally uniform current density is guaranteed on all parts. These two demands must be fulfilled by the apparatus being used. A further significant condition for achieving faultless metal coatings with a uniform layer thickness is the adequate mixing of the goods for galvanizing during the galvanic processing. This mixing of the goods for galvanization is usually obtained by turning the goods vessel around a non-perpendicular axis so that dependent on the shape and wall friction, the individual parts are conveyed up to a greater or lesser distance on the goods tray and then in turn will roll back down or slide down the tray. However, despite this goods movement, a good electrical contact and a gentle treatment of the goods for galvanization should be guaranteed. Also, for quantitatively high-grade metal coatings, additional requirements or demands are made and these are requirements for an adequate electrolyte exchange, an optimally unimpeded current transfer between the anodes and the goods being galvanized and an adequate size and surface for the anode in relation to the surfaces of the goods being treated.
The simplest vessel for goods is the electroplating bell or a rotatable pot, which simultaneously serves as a plating tank. A mixing of the goods for galvanization is achieved in that the bell is mounted with its axis inclined relative to the perpendicular and is rotated around this axis. Since the anode is suspended into the bell, the anode surface itself is usually too small in comparison to the surface of the goods given an employment of profiled special anodes. This, however, then leads to low deposition rates and thus, to a lengthening of the electroplating duration and to an increase of the abrasion on the parts.
Electroplating drums are also frequently employed for mass electroplating and these drums in contrast to the bell only serves as vessels for the goods and are arranged in a plating tank. A mixing of the goods for galvanization is effected by turning the electroplating drum around a horizontal axis. Since the anodes are situated outside of the drum member, large anode surfaces can be obtained. On the other hand, a perforation must be introduced into the jacket of the drum member for the current passage between anodes and the goods for galvanization. However, for reasons of stability and in view of the size of the goods being plated or galvanized, the open cross section of these perforations, which is available for the current passage, is dimensioned so small that a considerable deterioration of the current passage will occur. This, however, then again leads to a low deposition rate and thus, to a lengthening of the electroplating duration or time and to an increase of the abrasion of the goods being treated.
German Patent No. 830,862 discloses an apparatus of the species initially cited wherein the goods are placed in a carrying dish which is provided with ribs on its inside. These ribs promote a uniform distribution of the bulk goods on the floor of the goods carrying dish. Given a rotation of the goods carrying dish, the ribs upwardly entrain the bulk goods so that a degree of spreading relative to the floor of the goods carrying dish is considerably enhanced by the ribs. Both the carrying dish for the goods as well as the vessel serving for the acceptance of the completely electroplated goods are pivotably seated around a common shaft that is seated above the plating tank so that both vessels can be brought into a mutual position to allow the bulk goods to be emptied from the goods carrying dish into an acceptance vessel which is then pivoted out of the electrolyte as the goods carrying dish is returned to the working position. The discharge of the completely electroplated goods, thus, involves a considerable outlay of time.
Aluminum deposited from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte is distinguished by its ductility, low number of pores, corrosion resistance and capabilities of being anodically oxidized. Since, due to the reaction with atmospheric oxygen and atmospheric humidity, the access of air will cause a considerable reduction of the conductivity and useful life of these electrolytes, the electroplating must be undertaken in a means operating under the exclusion of air. So that the access of air can also be prevented during loading and unloading of this apparatus which operates under a protective atmosphere that excludes air, inward transfer and outward transfer locks are also required and these are fashioned as gas locks, as liquid locks or as combined gas/liquid locks. In mass aluminization utilizing the aprotic, oxygen-free and water-free, aluminum-organic electrolyte, the additional problem of preventing the access of air to the electrolyte in so far as possible is also added to the difficulties already set forth.
U.S. Pat. No. 4,360,409, which is based on German Pat. No. 30 23 129, discloses an apparatus for electro-deposition of aluminum from an aprotic, oxygen-free and water-free, aluminum-organic electrolyte, wherein the electroplating drum rotates about its horizontal axis and is arranged in a plating tank which can be closed gas tight. The electroplating drum is provided with perforations and is surrounded by two anodes which can be adjusted so that they form an opening for the bulk goods to be emptied through. The loading of the electroplating drum occurs via a conveyor means leading into the inside of the plating tank through a lock and this conveyor means ends above a closable opening of the electroplating drum so that the opening and closing of the electroplating drum is undertaken from the outside. A discharge vessel is fashioned as an outward transfer lock and serves the purpose of emptying the electroplating drum. This discharge vessel is arranged below the plating tank and is in communications therewith via a blockable, tubular connecting member.
In the known apparatus for electro-deposition of aluminum, the problem of preventing the access of air to the electrolyte has been satisfactorily resolved. As in other apparatus for drum electroplating, a deterioration of the current passage between the anodes arranged outside of the drum member and the goods being plated and situated in the inside of the drum can, however, also occur.